Mommy's got her hands on the wheel.
The "wheel" is the steering wheel of a vehicle.
To have your "hands on the wheel" is to be paying attention and to be taking control and care of a situation.
In the US, a number of years ago, there was a song that popularized this idiom called, "Jesus, take the wheel." This phrase is a simple prayer-like request for divine intervention in a situation. This example phrase can be used both seriously and humorously.
The opposite idiom is "sleeping at the wheel" which means to dangerously not be paying attention or be in control.
My guess is that means, that mommy has got the situation under her control. Or she has got her behaviour under her control to be a "better example" for her son. Metaphor of control. Implying the "steering" wheel of a vehicle.
This is the right answer.